Here is a good lesson I learned years ago.
Anytime you make something liquid based (such as a soup, chili, stew, etc.) that has vegetables in it, make sure the vegetables are cooked prior to adding your liquid, otherwise you may get some of that raw flavor in your soup. Plus, sauteeing vegetables as opposed to just throwing them in your broth and boiling them gives a better flavor. With experience you will learn when to put vegetables in as each vegetable takes a different amount of time to cook. In other words, if you are using different vegetables, you will add them in stages. To further illustrate let's say you are making a vegetable soup and you have: carrots, fennel, eggplant, onions, celery, garlic, peppers and zucchini. Assuming your vegetables are cut in soup-size pieces, I would add them in the order listed, cooking each vegetable for a few minutes before adding the next one. I would add the onions, celery, garlic and peppers at the same time, finally adding the zucchini at the end prior to adding my broth or water. I would then simmer the mixture for about an hour to allow flavors to develop and you are done.